Compensating device for the determination of the direction of sounds according to the binaural method



March 4 1924. 1,485,513

E. LUBCKE COMPENSATING DEVICE .FOR THE DETERMINATION OF THE DIRECTION OF SOUNDS ACCORDING- TO THE BINAURAL METHOD H Filed Aug. 29, 1922 5 v v Fig. 1. v E

LII I/l III/l Patented Mar. 4, 1924.

UNHTED STATES 1,485,513 PATENT OFFICE.

ERNST Lt'IBcKE, or BREMEneERMAnY, Assrenon TO ATLAS WERKE .AKTIE'NGESELL- SCHAFT, or BREMEN, GERMANY.

COMPENSATING DEVICE FOR THE DETERMINATION OF THE DIREGTTON E SOUNDS ACCORDING TO THE BINAUR-AL METHOD.

App1ication filed August 29, 1922. Serial No. 585,042.

T 0 all whom it may concern:

Be it known that I, ERNST Lr'nsolrn, a citizen of the German Republic, residing at Bremen, Germany, have invented certain new and useful Improvements in Compensating Device for the Determination of the Direction of Sounds According to the Binaural Method (for which an application for patent has been filed in Germany on the 31st of August, 1921), of which the following is a specification.

. For the determination of the direction of sounds a binaural method is frequently used which consists in arranging at a determined distance apart two artificial receivers (for instance microphones) which are connected with telephones from which separate sound leads of variable lengths are conducted to the ears of the observer. According to the time intervals between the arrival of the sound at the one ear and at the other car the operator has the impression as it the source of sound was situated more or less to one side. In order to measure the true direction of sound the time intervals are compensated by altering the sound ways between telephones and ears. At this compensating the observer has the impression that the source of sound which appeared to be situated at one side is moved further towards a point directly in front of him. If the time interval is Zero the impression received is exactly a middle impression, viz, the source of sound seems to be situated exactly in front. The apparatus can be adjusted very accuratelyv according to this middle impression. The variation of the sound path which is necessary for the production of the middle impression serves as measure for the direc tion of sound.

It has been known hitherto to effect this variation of the length of the air path by rotating one plate above another plate having circular channels as air paths. With such devices the telephones were not movable with the movable plates and the sound coming from the telephones entered into the circular channels by pierced members fixed to the stationary plate. Thus the sound from the telephone after having entered the one channel had to travel along same had to return and to travel back by another channel situated concentrically to the first channel before leaving the plates by the named pierced members and passing to the car of the observer. During passing through the pierced members the direction of sound was abruptly changed, the sound leaving the plate in a direction perpendicular to the plan of the circular channels. By this alternation of the direction of sound first by "returning and secondly in the pierced members so called stationary'sound waves were created which disturbed the soundimage in the head of the observer so that the latter was not able fully to ascertain the true position of the source of sound.

These inconveniences are removed by the object of invention, where only one circular H sound channel is arranged, the telephones are mounted on the movable plate and the sound from the circular channel passes into stationary mouth pieces and from there into the tubes leading to the car of the observer not abruptly changed in its direction but by a smooth arc. Thus offensive stationary waves cannot be created in the interior of the sound channel and the observer gets quite a distinct sound image enabling him, clearly to ascertain the true position of the source of sound.

By the displacing of the telephone plate the sound path between the one telephone and the one mouth piece is shortened, the sound path between the other telephone and the other mouthpiece being lengthened at the same time. A scale is connected with the movable plate which permits to read the differences of the sound paths or directly the direction of the sound.

An embodiment of the invention is illustrated in the accompanying drawing wherein' longitudinal section on line I-I of Fig. 2.

Fig. 2 is a plan view partly in section of the compensating device, the scale disc being removed.

In Figures 1 and 2, P is a stationary plate in which a circular channel K is arranged which terminates in the mouth pieces M M P is a plate slidably mounted upon plate P and upon which the telephones T and T are mounted. Borings R in plate 1? connect the telephones with channel K. Between the two borings R an intermediary piece Z, ground into the channel K, is fixed upon the movable plate and designed to pre- Fig. 1 shows a compensating device in vent the sound from T getting to the mouth 'piece M and the sound from T getting to the mouth piece M Plate P is revoluble around a spindle A. The relative oscillation of the movable plate with regard to the stationary plate is indicated by a hand F upon a scale S.

The invention is obviously not limited to a compensating device with circular channels K, as these channels can have any convenient shape, the movement of plate P being adapted to the shape of the channel.

The operation of the compensating device is as follows: Let us suppose the sound arrived sooner in the receiver connected with T than in the receiver connected with T and the left ear be connected with M by a flexible tube, the right ear being connected with 11 by a flexible tube of the equal length. The sound will evidently arrive sooner at the left ear than at the right car, if the compensator is in the position shown in the drawing, as the distance over which the sound has to travel between T and the left ear is equally long as that over which the sound has to travel between T and the right ear. The observer will therefore have the impression as if the source of sound were situated at a certain angle to the left hand side. In order to compensate the time interval between the arrivals of the sound in the two ears the movable telephone plate has to be turned in clockwise direction, whereby the sound path between T and M is lengthened and that between T and M shortened. The observer receives at this compensating movement the impression as if the source of sound moved towards the middle from its original position at one side. The apparatus is now adjusted so that the accurate middle impression is produced. From the scale the difference between the sound paths can be read wherefrom the direction of sound can be easily determined by calculation. The scale S is preferably gauged directly in angular degrees so that the direction of sound can be read directly.

1. A compensating device for the determination of the direction of sounds according to the binaural method with separate sound paths of variable length leading to the ears of the observer, comprising in combination a stationary plate having one annular channel which merges into two mouth pieces with a smooth rounding, a movable plate covering the stationary plate and carrying the telephones adapted to alter by its revolution the length of each part or the said channel between the telephones which move with said plate and the stationary mouth pieces of the said channel.

:2. A compensating device for the determination of the direction of sounds according to the binaural method with separate sound paths of variable length leading to the ears of the observer, comprising in combination a stationary circular plate having a circular channel which merges into two mouth pieces with a smooth rounding, a movable disc over the stationary plate, an intermediary piece fixed to said disc sliding in the stationary plate and dividing said channel into two parts, and means for showing the position of the movable disc with regard to the stationary plate.

3. A compensating device for the deter mination of the direction of sounds according to the binaural method with separate sound paths of variable length leading to the ears of the observer, comprising in combination a stationary circular plate having a circular channel which merges into two mouth pieces with a smooth rounding, a movable disc covering the stationary plate and carrying the telephones, an intermediary piece fixed to said disc between the tele phones sliding in the annular channel and dividing the latter into two parts, a scale plate secured to the movable disc, a hand in connection with the stationary plate and showing on the scale plate the position of the movable disc regarding to the stationary plate.

In testimony whereof I affix my signature in presence of two witnesses.

ERNST LUBCKE.

VJitnesses FRANCIS J. DUGAN, T. BRUENING. 

